In a number of applications, such as product packaging or other closed systems, corrodible items must be protected from reacting with their environment and losing their effectiveness or value during packaging, handling, transportation or end use. As would be expected, the most common example of such corrosion is that of metal items which tend to corrode, i.e., oxidize, pit, tarnish, mottle or discolor, in the presence of oxygen and moisture. Because both oxygen and water vapor are abundantly available under normal atmospheric and ambient conditions, precautions are necessary when packaging or otherwise using certain metal items. Items formed from iron, steel, copper, brass, aluminum, silver, and many alloys of such metals, are susceptible to such corrosion, as are materials with sacrificial or aesthetic coatings such as zinc or cadmium.
One method of protecting corrodible items has been to provide a package or other enclosure which includes one or more uncontained corrosion inhibiting compounds along with the corrodible item or items. Such corrosion inhibitors can include solids and liquids, and can be used in a number of ways. In some applications, the corrodible items are thoroughly coated with a corrosion inhibiting compound in the form of a solid, or a liquid, or a grease or a paste and then packaged or enclosed in closed containers. Although some degree of corrosion protection results, the presence of such coating on the corrodible items has obvious handling and packaging disadvantages.
Solid corrosion inhibitors, e.g. powders, pills or tablets, present a different set of disadvantages. Particulate materials can foul certain mechanical items, be aesthetically displeasing, and can be difficult to remove from the protected items when they are finally unpacked or otherwise put to use. Moreover, the types of chemicals necessary for inhibiting corrosion are often somewhat hazardous to persons if they are inhaled or come into contact with their skin.
In other applications, solid phase or liquid phase compounds are used which are generally referred to as vapor phase inhibitors (VPI) or, as used herein, volatile corrosion inhibitors (VCI). Such compounds emit vapors which protect corrodible substrates by depositing a protective coating upon the substrates. Because molecules in the vapor phase disperse very rapidly, even at ambient conditions or even cooler temperatures, a vapor phase corrosion inhibitor will generally set up an equilibrium environment rather quickly. In such an environment, the corrosion inhibiting compounds provided by the volatile corrosion inhibitors (VCI) can reach and protect all of the items in the enclosed environment much more efficiently than could solids or liquids, that are only effective when in contact with the corrodible substrate. Additionally, because of their rapid dispersal, removal of the protective vapors emitted from volatile corrosion inhibits from the items is unnecessary when the items themselves are removed from their respective packages or otherwise put to use.
Several techniques for using volatile corrosion inhibitors have evolved to date. One method comprises forming a tablet or some other solid shaped element from a solid compound which will either sublime into, or chemically release, the vapor phase corrosion inhibitor. In other techniques package walls or other substrates are painted or coated with volatile corrosion inhibitor-containing compositions which release protective vapors. Other techniques blend volatile corrosion inhibitor compounds with or impregnate them into materials such as foamed or foamable compositions so that a foamed article results which protects the items from physical shock, as well as from corrosion.
Generally speaking, some of the liquid or solid corrosion inhibiting compounds used in such techniques include triazoles; organic or inorganic nitrites, nitrates, carbonates, phosphates; primary, secondary, tertiary, or quaternary amines (aliphatic or aromatic) or their organic or inorganic acid salts. It will be understood, however, that such techniques can use other appropriate compounds, as well as those listed herein.
All of these methods suffer from at least one common disadvantage: the volatile corrosion inhibitors tend to produce, decompose into or otherwise leave behind a visible residue of chemicals. Such residues present a number of problems. First, the residual chemicals may cause health problems when they come in contact with a person's skin or are inhaled. Second, the residue can cause handling and mechanical problems, and third, the nature of some volatile corrosion inhibitors is such that they may react with some packaging materials or substrates with which they come in contact or to which they are applied. In other words, when blended with or impregnated into foams or applied to paper or other packaging materials, they may cause the materials to decompose, thereby aggravating the attendant problems listed above, or adding new problems; e.g. reduced shelf life.
Accordingly, there exists a need for a product and method for introducing volatile corrosion inhibitors inside closed packages or other enclosures which will provide the volatile corrosion inhibitors best suited for protecting packaged items, which will not react with the packaging material itself, and which will not form or otherwise leave behind a residue which must be eliminated or avoided during later unpacking, handling and finishing of the corrodible items. These volatile corrosion inhibitors may be accompanied with a desiccant so as to reduce the quantity of water vapor present in the package or other enclosure.
It is therefore an object of the present invention to provide a product which effectively distributes a volatile corrosion inhibitor within a package or another enclosure to effectively inhibit corrosion of items therein.
It is another object of the invention to provide a volatile corrosion inhibitor in a form which leaves no disadvantageous solid residue to cause later problems in the handling of the package, the enclosure, or the packaged or enclosed items.
It is a further object of this invention to provide a simple and easily accomplished method of adding volatile corrosion inhibitors to packages or enclosures and which is effective for a large number of different sizes and types of packages or enclosures and yet which requires very little in the way of customization or other specific tailoring.
It is yet a further object of the present invention to provide a simple and easily accomplished method of adding volatile corrosion inhibitors to packages or other enclosures, and wherein the volatile corrosion inhibitor may be packaged with a desiccant so as to reduce the quantity of water vapor present in the package or enclosure.